1. Field of the Invention
The invention relates to a method for material machining by way of laser, in particular for laser engraving with which the laser beam in tracks is led over a section of a surface of a subject to be machined, whereupon the subject is moved in order to bring a neighboring section of the subject into the machining field of the laser, over which then the laser beam is again led in tracks.
2. Description of the Related Art
With the two-dimensional laser micromaterial machining of subjects according to the state of the art, such as for example is known from DE 42 09 933, the tracks of the laser beam at neighboring sections meet or contact on a separating line when a field must be machined which is greater than the machining field of the used scanner head. At the resulting separating and bordering lines with the overlapping of the laser impulses with the machining of the individual regions there occurs an increased material removal, and with a contact or insufficient overlapping a reduced material removal. In both cases the separating lines between the individual regions become clearly visible which is generally not desired. In the case of three-dimensional engraving as a rule the volume to be taken away is removed is layers, wherein the above described effect is amplified even further. FIG. 1 shows the above described state of the art.
The object of the invention lies in improving the initially mentioned method so that no separating lines or transition regions are visible at the bordering regions of a field of a subject to be engraved.
The solution of this object lies in a method for material machining, in particular laser engraving, in which the laser beam is guided in tracks over a section of a surface of a subject to be machined, whereupon the subject is moved such that a neighboring section of the subject comes into the machining field of the laser over which the laser beam is then guided again in tracks. At the borders of neighboring sections of the subject there is formed an overlapping region whose machining is allocated to the one or to the other section such that the tracks in which the laser beam is guided on the respective section intermesh in the overlapping region.
With a two-dimensional machining, i.e. only a single layer is removed, the surface to be machined is divided into several sections in the form of a grid. With a focal width of the scanner of approx. 100 mm the section to be engraved has a size of approx. 70xc3x9770 mm2. In order to avoid the problem of the recognizable sharp separating or border line, on joining together the bordering regions according to the invention there is formed an overlapping region which on both sides of the common section border concerned is wider than the laser track.
The individual tracks of the laser machining end within this overlapping region and not on the common border line of the sections; the system or the device for carrying out the method according to the invention however notices where the individual machining track ends in order to connect thereto in the next section in a xe2x80x9cseamlessxe2x80x9d manner. In this way there no longer occurs any optically recognizable transition line but within the overlapping region a non-uniform distribution of transition points which in the overlapping region preferably are completely statistically distributed, wherein the distribution may also be fixed by the user of the machining means. As long as the transition points are distributed in a sufficiently unordered manner, they are no longer perceived as an optical defect and are thus no longer recognizable as a separating or border line.
In order in the case of three-dimensional machining to avoid a disadvantageous effect of layers applied over one another, a section is not completely machined, i.e. the removal volume is not removed in the whole depth but in the whole machining field in layers, i.e. in all sections the material is first removed from a first layer and thus all transitions of the first layer created. Thereafter a second layer is machined or removed, and specifically the direction of the parallel laser tracks of the second layer is rotated by any angle to the laser tracks of the first layers so that there does not occur any systematic excesses of the deepening. Just as with the described one-layer machining the transition points of the second and further layers of each section also lie in an overlapping region either distributed about the same, or also a displaced or rotated section border. In this way one removes layer for layer without the transition regions becoming visible.
If the number of layers is large enough it is also sufficient to provide overlapping regions in a few of the last layers to be removed in the manner according to the invention, whilst border regions in the first layers may joined to one another in a conventional manner.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.